1. Field of the Invention
The present invention relates to a safety syringe in which the needle is retractable after injection.
2. Description of the Prior Art
Various types of disposable syringes are widely used nowadays. After discarded, large amount of such syringes result in problem of pollution of environment. The used syringes often impale medical personnel and infect the personnel with viruses or bacteria carried by the patients. Especially, in case the medical personnel are infected with AIDS virus, the personnel may die innocently.
In order to solve these problems, various types of retractable syringes have been developed. For example, a spring is installed between the syringe barrel and the piston for pulling the needle back into the barrel after injection. However, due to the property of the liquid medicine, the material of the spring is strictly limited. Therefore, the structure of such syringe is complicated and the manufacturing cost is very high. Various types of safety syringes free from the springs have been also developed. In such syringe, a latch member is disposed at the bottom of the barrel, whereby when the plunger is pushed to the bottom of the barrel, the latch member latches the plunger with the needle. Therefore, when the plunger is pulled back, the needle is retracted into the barrel along with the plunger so as to avoid impalement of the medical personnel or other persons.
As of the present time, all the existing safety syringes must be used with specifically designed and manufactured injection needles which cannot be replaced. Therefore, the suppliers must manufacture various kinds of safety syringes and injection needles.